A3938
Three-Phase Power MOSFET Controller
VBB. Motor power supply connection for the A3938 and
for power MOSFETs. It is good practice to connect a decou-
DEAD. Analog input. A resistor between DEAD and LCAP
is selected to adjust turn-off time to turn-on time. This
pling capacitor from this pin to AGND, as close to the device delay is needed to prevent cross-conduction in the external
pins as possible.
power MOSFETs. See the section Application Information
for details on setting dead time.
REF. Analog input to current limit comparator. Voltage
applied here sets the peak load current according to the fol-
lowing equation:
SENSE. Analog input to the current limit comparator.
Voltage representing load current appears on this pin. Voltage
transients that are seen at this pin when the drivers turn on
ITRIP = VREF / RSENSE
are ignored for period of time, tBLANK
.
AGND. Analog reference ground.
LCAP. 5 V reference to power internal logic and provide
low current for DEAD pin and FAULT pin. Connection for
0.1 µF external capacitor for decoupling.
PGND. Return for low-side gate drivers. This should be
connected to the PCB power ground.
Commutation Truth Table
H1
1
1
1
0
0
0
1
1
1
0
0
0
H2
0
0
1
1
1
0
0
0
1
1
1
0
H3
1
0
0
0
1
1
1
0
0
0
1
1
DIR
1
1
1
1
1
1
0
0
0
0
0
0
GLA
0
0
1
1
0
0
1
0
0
0
0
1
GLB
0
0
0
0
1
1
0
1
1
0
0
0
GLC
1
1
0
0
0
0
0
0
0
1
1
0
GHA
1
0
0
0
0
1
0
0
1
1
0
0
GHB
0
1
1
0
0
0
0
0
0
0
1
1
GHC
0
0
0
1
1
0
1
1
0
0
0
0
SA
HI
Z
LO
LO
Z
HI
LO
Z
HI
HI
Z
SB
Z
HI
HI
Z
LO
LO
Z
LO
LO
Z
SC
LO
LO
Z
HI
HI
Z
HI
HI
Z
LO
LO
Z
HI
HI
LO
Input Logic
MODE
PWM
RESET
Quadrant
Mode of Operation**
PWM chop – current decay with opposite of selected low-
side drivers ON.
Selected drivers ON. If current limiting, opposite of selected
low-side drivers ON.
0*
0*
0
1
0
Fast decay
0
Fast Decay
1
1
0
1
0
0
Slow decay PWM chop – current decay with both low-side drivers ON.
Slow Decay Selected drivers ON. If current limiting, both low-side drivers ON.
All high-side drivers OFF, low-sides see BRKSEL stored.
Clears storable faults.
X
X
1
X
* Low-side, only, Synchronous Rectification mode.
**See Commutation Truth Table for meaning of “both” and "selected."
6
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